Regarding a brushless motor, there is known a method of adjusting induced voltage for each phase into a trapezoidal wave in which an odd-order harmonic is superimposed on a fundamental wave, thereby improving output and efficiency as compared to the case of using a fundamental wave alone.
Patent Document 1 proposes a method of adjusting induced voltage for each phase into a trapezoidal wave in which an odd-order harmonic is superimposed, thereby improving torque.
In this document, induced voltage adjustment means superimposes a third-order harmonic on induced voltage having a sine waveform which is a fundamental wave, thereby adjusting induced voltage for each phase into a trapezoidal waveform.
As a result, the shape of a part surrounded by a characteristic curve of induced voltage for each phase with respect to a rotor rotation angle, and the horizontal axis (rotation angle), becomes a shape that is flattened and broadened as compared to the case of a characteristic curve based on a fundamental wave alone, whereby motor generated torque increases.
Patent Document 2 describes that induced voltage of a motor is set to have a waveform containing a third-order harmonic, whereby motor output can be improved as compared to the case of sine wave, while vibration and noise are reduced.